Folded Waveugide Traveling-Wave Tube with Frequency-Selective Attenuator

This paper reports a beam-wave interaction model with folded waveguide and frequency-selective attenuator. Four-cut split ring resonator and metal-substrate-metal structure are adopted to form the frequency-selective structure. The attenuator is designed to selectively attenuate the backward wave. Favorable transmission around the operating frequency can be achieved by the proposed attenuator. The wave in the input section can participate in the interaction in the output section. The PIC simulation shows that 66.7 W stable output power can be achieved by metamaterial-loaded interaction circuit. The output and reflection signals are stable for more than 20 ns without obvious oscillation, meaning for the effective suppression of the backward-wave oscillation.